WO2023008005A1

WO2023008005A1 - Positive electrode material and battery

Info

Publication number: WO2023008005A1
Application number: PCT/JP2022/025012
Authority: WO
Inventors: 勇祐西尾; 賢治長尾; 出佐々木
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2021-07-27
Filing date: 2022-06-23
Publication date: 2023-02-02
Also published as: CN117693828A; EP4379831A1; US20240145725A1; JPWO2023008005A1

Abstract

This positive electrode material 1000 comprises a mixture of a positive electrode active material 110, a solid electrolyte 100 and a conductive material 140. The conductive material 140 contains a first conducive material 150 that has an average major axis diameter of 1 µm or more and a second conductive material 160 that has an average particle diameter of 100 nm or less. The ratio of the volume of the positive electrode active material 110 to the total volume of the positive electrode active material 110 and the solid electrolyte 100 is 60% to 90%.

Description

Cathode materials and batteries

The present disclosure relates to cathode materials and batteries.

Patent Document 1 discloses a solid battery having a positive electrode containing an active material, a fibrous conductive material, a granular conductive material, and a solid electrolyte.

WO2020/130069

In the conventional technology, it is desired to achieve both energy density and electronic conductivity in the positive electrode.

In one aspect of the present disclosure, the positive electrode material comprises:
comprising a mixture of a positive electrode active material, a solid electrolyte and a conductive material;
The conductive material includes a first conductive material having an average major axis diameter of 1 μm or more and a second conductive material having an average particle size of 100 nm or less,
A ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 60% or more and 90% or less.

According to the present disclosure, both energy density and electronic conductivity can be achieved in the positive electrode.

FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material in Embodiment 1. FIG. 2 is a cross-sectional view showing a schematic configuration of a positive electrode material in Modification 1. FIG. FIG. 3 is a cross-sectional view showing a schematic configuration of a battery according to Embodiment 2. FIG. FIG. 4 is a diagram explaining a method for evaluating the electron conductivity of the positive electrode. 5 is a graph showing the correlation between the voltage and the current value in the opposing positive electrode of Example 1. FIG. 6 is a graph showing the electron conductivity of the positive electrodes of Examples 1 to 9 and Comparative Examples 1 to 5. FIG.

(Findings on which this disclosure is based)
Patent Document 1 discloses a solid battery having a positive electrode containing an active material, a fibrous conductive material, a granular conductive material, and a solid electrolyte. Patent Document 1 describes that in the positive electrode material, the amount of the active material is about 60 parts by mass with respect to the total amount of 100 parts by mass of the active material, the fibrous conductive material, the granular conductive material, and the solid electrolyte. ing. That is, in the positive electrode material of Patent Document 1, the ratio of the volume of the active material to the total volume of the active material, the fibrous conductive material, the granular conductive material, and the solid electrolyte is about 43%. Thus, in the positive electrode material of Patent Document 1, the volume ratio of the electronically insulating solid electrolyte is larger than the volume ratio of the active material. Therefore, when the positive electrode material of Patent Document 1 is used, it is difficult to ensure sufficient electron conductivity in the positive electrode. On the other hand, when the ratio of the conductive material is increased to ensure electronic conductivity, the ratio of the active material is decreased, so the energy density of the positive electrode is lowered.

The inventors have conducted extensive research on methods for reducing the resistance of all-solid-state lithium-ion batteries. As a result, the inventors have found that improving the electronic conductivity of the positive electrode reduces the resistance of the battery. It is presumed that this is largely due to the resistance between the positive electrode and the current collector. Furthermore, the present inventors have found that if the ratio of the conductive material is increased too much to improve the electronic conductivity, not only does the energy density of the battery decrease, It was found that the lithium ion conduction between When lithium ion conduction is inhibited, the reaction resistance of the positive electrode active material increases. Based on these findings, the present inventors discovered a positive electrode material capable of achieving both energy density and electronic conductivity in the positive electrode.

(Overview of one aspect of the present disclosure)
The positive electrode material according to the first aspect of the present disclosure is
comprising a mixture of a positive electrode active material, a solid electrolyte and a conductive material;
The conductive material includes a first conductive material having an average major axis diameter of 1 μm or more and a second conductive material having an average particle size of 100 nm or less,
A ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 60% or more and 90% or less.

According to the above configuration, since the volume ratio of the positive electrode active material is larger than the volume ratio of the solid electrolyte, the energy density in the positive electrode can be improved. Moreover, since the first conductive material has an average major axis diameter of 1 μm or more, the first conductive material and the second conductive material are easily connected to each other in the positive electrode. Therefore, an electron-conducting network can be efficiently formed in the positive electrode. Thereby, both the energy density and the electronic conductivity can be achieved in the positive electrode.

In the second aspect of the present disclosure, for example, in the positive electrode material according to the first aspect, the volume ratio of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 65% or more and 85% or less. may According to the above configuration, it is possible to further improve the energy density in the positive electrode.

In the third aspect of the present disclosure, for example, in the positive electrode material according to the first aspect, the ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 67% or more and 75% or less. may According to the above configuration, it is possible to further improve the energy density in the positive electrode.

In the fourth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to third aspects, when the mass ratio of the positive electrode active material is 100, the mass ratio of the conductive material is 3 It may be below. According to the above configuration, it is possible to suppress inhibition of lithium ion conduction between the positive electrode active material and the solid electrolyte due to the conductive material.

In the fifth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to fourth aspects, the ratio of the mass of the second conductive material to the mass of the conductive material is 80% or less. There may be. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the sixth aspect of the present disclosure, for example, in the positive electrode material according to the fifth aspect, the ratio of the mass of the second conductive material to the mass of the conductive material may be 5% or more and 50% or less. . According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the seventh aspect of the present disclosure, for example, in the positive electrode material according to the fifth aspect, the ratio of the mass of the second conductive material to the mass of the conductive material may be 6% or more and 25% or less. . According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the eighth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to seventh aspects, the first conductive material may have an average major axis diameter of 4 μm or more. According to the above configuration, a conductive path that enables long-distance electron conduction in the positive electrode is easily formed by the first conductive material. Thereby, the electron conductivity in the positive electrode can be further improved.

In the ninth aspect of the present disclosure, for example, in the positive electrode material according to the eighth aspect, the second conductive material may have an average particle size of 25 nm or less. According to the above configuration, it becomes easier for the second conductive material to adhere to the surface of the positive electrode active material. Therefore, by connecting the first conductive material and the second conductive material, an electron-conducting network is likely to be formed in the positive electrode.

In the tenth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to ninth aspects, the first conductive material and the second conductive material may contain a carbon material. . According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the eleventh aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to tenth aspects, the first conductive material may contain a fibrous carbon material. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the twelfth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to eleventh aspects, the second conductive material may contain carbon black. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the thirteenth aspect of the present disclosure, for example, in the positive electrode material according to the twelfth aspect, the carbon black may contain acetylene black. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

In the fourteenth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to thirteenth aspects, the solid electrolyte is at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte may contain According to the above configuration, it is possible to improve the output characteristics of the battery.

In the fifteenth aspect of the present disclosure, for example, in the positive electrode material according to any one of the first to fourteenth aspects, the positive electrode active material may have a layered rock salt structure. In the layered rock salt structure, transition metals and lithium are regularly arranged to form a two-dimensional plane, so lithium can diffuse two-dimensionally. Therefore, according to the above configuration, the energy density of the battery can be improved.

In the sixteenth aspect of the present disclosure, for example, the positive electrode material according to any one of the first to fifteenth aspects may further include a coating layer that covers at least part of the surface of the positive electrode active material. According to the above configuration, the resistance of the battery can be further reduced.

The battery according to the seventeenth aspect of the present disclosure includes
a positive electrode comprising the positive electrode material according to any one of the first to sixteenth aspects;
a negative electrode;
an electrolyte layer provided between the positive electrode and the negative electrode;
Prepare.

According to the above configuration, it is possible to achieve both energy density and electronic conductivity in the positive electrode. Thereby, the energy density of the battery can be improved and the resistance of the battery can be lowered.

In the eighteenth aspect of the present disclosure, for example, in the battery according to the seventeenth aspect, the electrolyte layer may contain a sulfide solid electrolyte. According to the above configuration, it is possible to improve the output characteristics of the battery.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

(Embodiment 1)
[Positive material]
FIG. 1 is a cross-sectional view showing a schematic configuration of a positive electrode material 1000 according to Embodiment 1. FIG.

The positive electrode material 1000 includes a mixture of a positive electrode active material 110, a solid electrolyte 100 and a conductive material 140. The conductive material 140 includes a first conductive material 150 having an average major axis diameter of 1 μm or more and a second conductive material 160 having an average particle size of 100 nm or less. The ratio of the volume of positive electrode active material 110 to the total volume of positive electrode active material 110 and solid electrolyte 100 is 60% or more and 90% or less.

According to the above configuration, since the volume content of the positive electrode active material 110 is higher than the volume content of the solid electrolyte 100, the energy density of the positive electrode can be improved. Also, since the first conductive material 150 has an average major axis diameter of 1 μm or more, the first conductive material 150 and the second conductive material 160 are easily connected in the positive electrode. Therefore, an electron-conducting network can be efficiently formed in the positive electrode. Thereby, both the energy density and the electronic conductivity can be achieved in the positive electrode.

The average major axis diameter of the first conductive material 150 can be measured, for example, using a scanning electron microscope SEM image. Specifically, the average major axis diameter is obtained by calculating the average major axis diameter of 20 arbitrarily selected particles of the first conductive material 150 using the SEM image. Here, the major axis diameter of the first conductive material 150 is defined as the diameter of the circle with the smallest area surrounding the particles of the first conductive material 150 in the SEM image of the particles of the first conductive material 150 .

The average particle size of the second conductive material 160 can be measured, for example, using a TEM image obtained by a transmission electron microscope (TEM). Specifically, the average particle diameter is obtained by calculating the average value of the equivalent circle diameters of 20 arbitrarily selected particles of the second conductive material 160 using a TEM image.

Here, the average length axis of the first conductive material and the average particle diameter of the second conductive material contained in the positive electrode material can be measured, for example, as follows. First, the positive electrode material is obtained by, for example, scraping off the positive electrode material from the battery so as not to mix the negative electrode material. The obtained positive electrode material is mixed with water for dissolving the solid electrolyte, and filtered to extract the active material other than the solid electrolyte, the binder, and the conductive material. Next, the active material, binder, and conductive material taken out are mixed with an organic solvent such as toluene to dissolve the binder, and filtered to take out the active material and conductive material. Furthermore, the active material and conductive material taken out are mixed with an acid aqueous solution to dissolve the active material, and filtered to take out the conductive material. After that, the removed conductive material is dried. By using the dried conductive material, the average major axis diameter of the first conductive material can be measured based on the SEM image as described above, and the average grain size of the second conductive material can be measured based on the TEM image. Diameter can be measured.

The volume ratio of the positive electrode active material 110 to the total volume of the positive electrode active material 110 and the solid electrolyte 100 can be calculated, for example, by the following method. The positive electrode active material 110 contained in the positive electrode material 1000 can be taken out, for example, by dissolving only the solid electrolyte 100 using a solvent. The total mass of positive electrode active material 110 and solid electrolyte 100 and the mass of positive electrode active material 110 can be obtained from the masses before and after the dissolution. The respective specific gravities of the positive electrode active material 110 and the solid electrolyte 100 can be known from literature and the like. From these values, the ratio of the volume of positive electrode active material 110 to the total volume of positive electrode active material 110 and solid electrolyte 100 can be calculated.

The volume ratio of the positive electrode active material 110 to the total volume of the positive electrode active material 110 and the solid electrolyte 100 may be 65% or more and 85% or less. According to the above configuration, it is possible to further improve the energy density in the positive electrode.

The volume ratio of the positive electrode active material 110 to the total volume of the positive electrode active material 110 and the solid electrolyte 100 may be 67% or more and 75% or less. According to the above configuration, it is possible to further improve the energy density in the positive electrode.

When the mass ratio of the positive electrode active material 110 is 100, the mass ratio of the conductive material 140 may be 3 or less. According to the above configuration, it is possible to suppress inhibition of lithium ion conduction between positive electrode active material 110 and solid electrolyte 100 by conductive material 140 .

The mass ratio of the conductive material 140 when the mass ratio of the positive electrode active material 110 is 100 can be calculated, for example, by the following method. The mass of the positive electrode active material 110 contained in the positive electrode material 1000 can be obtained by the method described above. The mass of conductive material 140 included in cathode material 1000 can be obtained, for example, from mass reduction due to high temperature pyrolysis. From these values, the mass ratio of the conductive material 140 when the mass ratio of the positive electrode active material 110 is 100 can be calculated.

The ratio of the mass of the second conductive material 160 to the mass of the conductive material 140 may be 80% or less. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The ratio of the mass of the second conductive material 160 to the mass of the conductive material 140 can be calculated, for example, by the following method. The mass of the second conductive material 160 relative to the mass of the conductive material 140 can be obtained by particle size distribution measurement, classification, or the like for the conductive material 140 taken out by the method described above. In this way, the ratio of the mass of second conductive material 160 to the mass of conductive material 140 can be calculated.

The ratio of the mass of the second conductive material 160 to the mass of the conductive material 140 may be 5% or more and 50% or less. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The ratio of the mass of the second conductive material 160 to the mass of the conductive material 140 may be 6% or more and 25% or less. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

(Conductive material)
First conductive material 150 and second conductive material 160 may include a carbon material. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The first conductive material 150 and the second conductive material 160 may be carbon materials. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The first conductive material 150 may contain a fibrous carbon material. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The first conductive material 150 may be a fibrous carbon material. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

Examples of fibrous carbon materials include fibrous carbon such as vapor-grown carbon fiber, carbon nanotube, and carbon nanofiber. When first conductive material 150 includes a fibrous carbon material, first conductive material 150 may include any one of these materials, or two or more of these materials. You can When first conductive material 150 is a fibrous carbon material, first conductive material 150 may be composed of any one of these materials, or composed of two or more of these materials. may

The second conductive material 160 may contain carbon black. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The second conductive material 160 may be carbon black. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

Carbon black includes acetylene black and ketjen black. When the second conductive material 160 contains carbon black, the second conductive material 160 may contain acetylene black or may contain ketjen black. The second conductive material 160 may contain both acetylene black and ketjen black. When the carbon black contains acetylene black, it is possible to further improve the electron conductivity of the positive electrode. When the second conductive material 160 is carbon black, the second conductive material 160 may be acetylene black or Ketjen black. The second conductive material 160 may be composed of acetylene black and ketjen black.

When the first conductive material 150 is a fibrous carbon material, the first conductive material 150 contains the fibrous carbon material as a main component and further includes unavoidable impurities or synthesizes the fibrous carbon material. It may contain starting materials, by-products, decomposition products, and the like that are used in practice. In the present disclosure, "main component" means the component contained in the largest amount in terms of mass ratio.

The first conductive material 150 may contain, for example, 100% of the fibrous carbon material in terms of mass ratio to the entire first conductive material 150, except for impurities that are unavoidably mixed.

Thus, the first conductive material 150 may be composed only of the fibrous carbon material.

When the second conductive material 160 is carbon black, the second conductive material 160 contains carbon black as a main component, and further contains unavoidable impurities or starting materials used when synthesizing carbon black. , by-products and decomposition products.

The second conductive material 160 may contain, for example, 100% carbon black in terms of mass ratio with respect to the entire second conductive material 160, excluding impurities that are unavoidably mixed.

Thus, the second conductive material 160 may be composed of carbon black only.

The first conductive material 150 may have an average major axis diameter of 4 μm or more. According to the above configuration, the first conductive material 150 easily forms a conduction path that enables long-distance electron conduction to the positive electrode. Thereby, the electron conductivity in the positive electrode can be further improved.

The second conductive material 160 may have an average particle size of 25 nm or less. According to the above configuration, the second conductive material 160 easily adheres to the surface of the positive electrode active material 110 . Therefore, by connecting the first conductive material 150 and the second conductive material 160, an electron-conducting network is likely to be formed in the positive electrode.

The shape of the first conductive material 150 is not particularly limited as long as it has an average major axis diameter of 1 μm or more. The first conductive material 150 may be fibrous, acicular, or the like, for example. The shape of the first conductive material 150 may be fibrous.

The shape of the second conductive material 160 is not particularly limited as long as it has an average particle size of 100 nm or less. The second conductive material 160 may be spherical, oval, or the like, for example. The shape of the second conductive material 160 may be spherical.

The conductive material 140 may contain a conductive material different from the first conductive material 150 and the second conductive material 160 . Such conductive materials include graphites such as natural graphite or artificial graphite, metal fibers, carbon fluoride, metal powders such as aluminum, conductive whiskers such as zinc oxide or potassium titanate, and conductive materials such as titanium oxide. and conductive polymer compounds such as polyaniline, polypyrrole and polythiophene. According to the above configuration, it is possible to further improve the electron conductivity of the positive electrode.

The conductive material 140 may be composed of only the first conductive material 150 and the second conductive material 160. That is, conductive material 140 does not have to include a conductive material different from first conductive material 150 and second conductive material 160 .

(Positive electrode active material)
As the positive electrode active material 110, a material that can be used as a positive electrode active material for all-solid-state lithium ion batteries can be used. Examples of the positive electrode active material 110 include LiCoO ₂ , LiNi _x Me _1-x O ₂ , LiNi _x Co _1-x O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMnO ₂ , Li -Mn spinel, lithium titanate, lithium metal phosphate, and transition metal oxides. In LiNi _x Me _1-x O ₂ , x satisfies 0.5≦x<1, and Me includes at least one selected from the group consisting of Co, Mn and Al. In LiNi _x Co _1-x O ₂ , x satisfies 0<x<0.5. LiMn _1.5 Ni _0.5 O ₄ , LiMn _1.5 Al _0.5 O ₄ , LiMn _1.5 Mg _0.5 O ₄ , LiMn _1.5 Co _0.5 O ₄ , LiMn _1.5 Fe _0.5 O ₄ , and LiMn _1.5 Zn _0.5 as hetero-element-substituted Li—Mn spinels. _O4 can be mentioned. Lithium titanate includes Li ₄ Ti ₅ O ₁₂ . Lithium metal phosphates include _LiFePO4 , _LiMnPO4 , _LiCoPO4 , and _LiNiPO4 . Transition metal _oxides include _V2O5 and _MoO3 .

The positive electrode active material 110 includes LiCoO ₂ , LiNi _x Me _1-x O ₂ , LiNi _x Co _1-x O ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiMnO ₂ , Li— It may be a lithium-containing composite oxide selected from Mn spinel, lithium metal phosphate, and the like.

When the positive electrode active material 110 is a lithium-containing composite oxide, the positive electrode active material 110 may have a layered rock salt structure. In the layered rock salt structure, transition metals and lithium are regularly arranged to form a two-dimensional plane, so lithium can diffuse two-dimensionally. Therefore, according to the above configuration, the energy density of the battery can be improved.

(solid electrolyte)
Solid electrolyte 100 may contain at least one selected from the group consisting of sulfide solid electrolytes and halide solid electrolytes. According to the above configuration, it is possible to improve the output characteristics of the battery.

The solid electrolyte 100 may be a mixture of a sulfide solid electrolyte and a halide solid electrolyte.

Sulfide solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S—SiS ₂ , Li ₂ S—B ₂ S ₃ , Li ₂ S—GeS ₂ , Li _3.25 Ge _0.25 P _0.75 S ₄ , Li ₁₀ GeP ₂ S ₁₂ and the like are included. Also, a _sulfide solid electrolyte having an _Argyrodite structure, such _as _Li6PS5Cl , _Li6PS5Br , and _Li6PS5I , may be used. _LiX , _Li2O , _MOq , _LipMOq , etc. may be added to these sulfide solid electrolytes. Here, X is at least one selected from the group consisting of F, Cl, Br and I. Also, M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe and Zn. p and q are natural numbers respectively. One or more sulfide solid electrolytes selected from the above materials may be used.

According to the above configuration, the ionic conductivity of the sulfide solid electrolyte can be further improved. Thereby, the charge/discharge efficiency of the battery can be further improved.

A halide solid electrolyte is represented, for example, by the following compositional formula (1).

Li _α M _β X _γ Formula (1)

Here, α, β, and γ are independently values greater than 0. M contains at least one element selected from the group consisting of metal elements other than Li and metalloid elements. X includes at least one selected from the group consisting of F, Cl, Br, and I;

In the present disclosure, "metalloid elements" are B, Si, Ge, As, Sb and Te. "Metallic element" means all elements contained in Groups 1 to 12 of the periodic table except hydrogen, and B, Si, Ge, As, Sb, Te, C, N, P, O, S, and All elements contained in groups 13 to 16 of the periodic table except Se. That is, the term "semimetallic element" or "metallic element" refers to a group of elements that can become cations when an inorganic compound is formed with a halogen element.

The halide solid electrolyte represented by the compositional formula (1) has high ionic conductivity compared to a halide solid electrolyte such as LiI composed of Li and a halogen element. Therefore, according to the halide solid electrolyte represented by the compositional formula (1), the ionic conductivity of the halide solid electrolyte can be further improved.

In the composition formula (1), M may be at least one element selected from the group consisting of metal elements other than Li and metalloid elements.

In the composition formula (1), X may be at least one selected from the group consisting of F, Cl, Br and I.

The composition formula (2) may satisfy 2.5≦α≦3, 1≦β≦1.1, and γ=6. According to the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

In the composition formula (1), M may contain Y (= yttrium). That is, the halide solid electrolyte may contain Y as a metal element. According to the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

The halide solid electrolyte containing _Y may be, for example, _a compound represented by the composition _formula _LiaMebYcX6 . Here a+mb+3c=6 and c>0 are satisfied. Me is at least one element selected from the group consisting of metal elements excluding Li and Y and metalloid elements. m is the valence of the element Me. X is at least one selected from the group consisting of F, Cl, Br and I;

Me may be, for example, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta and Nb.

According to the above configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

For example, the following materials can be used as the halide solid electrolyte. According to the following configuration, the ionic conductivity of the halide solid electrolyte can be further improved.

The halide solid electrolyte may be a material represented by the following compositional formula (A1).

Li _6-3d Y _d X ₆ Formula (A1)

In the composition formula (A1), X is at least one selected from the group consisting of F, Cl, Br and I. Also, 0<d<2 is satisfied.

The halide solid electrolyte may be a material represented by the following compositional formula (A2).

Li ₃ YX ₆ Formula (A2)

In the composition formula (A2), X is at least one selected from the group consisting of F, Cl, Br and I.

The halide solid electrolyte may be a material represented by the following compositional formula (A3).

Li _3-3δ Y _1+δ Cl ₆ Formula (A3)

0<δ≦0.15 is satisfied in the composition formula (A3).

The halide solid electrolyte may be a material represented by the following compositional formula (A4).

Li _3-3 δ Y _{1+ δ} Br ₆ Formula (A4)

0<δ≦0.25 is satisfied in the composition formula (A4).

The halide solid electrolyte may be a material represented by the following compositional formula (A5).

_Li3-3δ _+aY1+ _δ- _aMeaCl6 _- _xyBrxIy Formula (A5)

In composition formula (A5), Me includes at least one selected from the group consisting of Mg, Ca, Sr, Ba and Zn. Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba and Zn.

In the composition formula (A5), -1 < δ < 2, 0 < a < 3, 0 < (3-3 δ + a), 0 < (1 + δ - a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and ( x+y)≦6 is satisfied.

The halide solid electrolyte may be a material represented by the following compositional formula (A6).

_Li3-3δY1 _+δ- _aMeaCl6 _- _xyBrxIy Formula ₍ A6)

In composition formula (A6), Me includes at least one selected from the group consisting of Al, Sc, Ga and Bi. Me may be at least one selected from the group consisting of Al, Sc, Ga and Bi.

In composition formula (A6), −1<δ<1, 0<a<2, 0<(1+δ−a), 0≦x≦6, 0≦y≦6, and (x+y)≦6 are satisfied .

The halide solid electrolyte may be a material represented by the following compositional formula (A7).

_Li3-3δ-aY1 ₊ _δ- _aMeaCl6 _- _xyBrxIy Formula (A7)

In composition formula (A7), Me includes at least one selected from the group consisting of Zr, Hf and Ti. Me may be at least one selected from the group consisting of Zr, Hf and Ti.

In the composition formula (A7), -1 < δ < 1, 0 < a < 1.5, 0 < (3-3 δ-a), 0 < (1 + δ-a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x+y)≦6 are satisfied.

The halide solid electrolyte may be a material represented by the following compositional formula (A8).

_Li3-3δ-2aY1 ₊ _δ- _aMeaCl6 _- _xyBrxIy Formula (A8)

In composition formula (A8), Me includes at least one selected from the group consisting of Ta and Nb. Me may be at least one selected from the group consisting of Ta and Nb.

In the composition formula (A8), -1 < δ < 1, 0 < a < 1.2, 0 < (3-3 δ-2a), 0 < (1 + δ-a), 0 ≤ x ≤ 6, 0 ≤ y ≤ 6, and (x+y)≦6 are satisfied.

As the halide solid electrolyte, more specifically, for example, Li ₃ YX ₆ , Li ₂ MgX ₄ , Li ₂ FeX ₄ , Li(Al, Ga, In) X ₄ , Li ₃ (Al, Ga, In) X ₆ , etc. can be used. Here, X is at least one selected from the group consisting of F, Cl, Br and I.

In the present disclosure, the notation "(A, B, C)" in the chemical formula means "at least one selected from the group consisting of A, B, and C". For example, "(Al, Ga, In)" is synonymous with "at least one selected from the group consisting of Al, Ga and In". The same is true for other elements.

The halide solid electrolyte does not have to contain sulfur. According to the above configuration, generation of hydrogen sulfide gas can be suppressed. Therefore, it is possible to realize a battery with improved safety.

The shape of the solid electrolyte 100 is not particularly limited. The shape of the solid electrolyte 100 may be, for example, needle-like, spherical, or oval. For example, the shape of the solid electrolyte 100 may be particulate.

For example, when the shape of the solid electrolyte 100 is particulate (eg, spherical), the median diameter of the solid electrolyte 100 may be 100 μm or less. When the median diameter of the solid electrolyte 100 is 100 μm or less, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000 . This improves the charge/discharge characteristics of the battery.

The median diameter of the solid electrolyte 100 may be 10 μm or less. According to the above configuration, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000 .

The median diameter of the solid electrolyte 100 may be smaller than the median diameter of the positive electrode active material 110 . According to the above configuration, the positive electrode active material 110 and the solid electrolyte 100 can form a better dispersion state in the positive electrode material 1000 .

The shape of the positive electrode active material 110 is not particularly limited. The shape of the positive electrode active material 110 may be, for example, acicular, spherical, or oval. For example, the shape of the positive electrode active material 110 may be particulate.

The median diameter of the positive electrode active material 110 may be 0.1 μm or more and 100 μm or less. When the median diameter of the positive electrode active material 110 is 0.1 μm or more, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersion state in the positive electrode material 1000 . This improves the charge/discharge characteristics of the battery. When the median diameter of the positive electrode active material 110 is 100 μm or less, the diffusion rate of lithium in the positive electrode active material 110 is sufficiently ensured. This allows the battery to operate at high output.

The median diameter of the positive electrode active material 110 may be larger than the median diameter of the solid electrolyte 100 . Thereby, the positive electrode active material 110 and the solid electrolyte 100 can form a good dispersed state.

In the present disclosure, the median diameter means the particle size (d50) when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured by, for example, a laser diffraction measurement device or an image analysis device.

In the positive electrode material 1000, the solid electrolyte 100 and the positive electrode active material 110 may be in contact with each other.

The positive electrode material 1000 may contain a plurality of solid electrolyte 100 particles and a plurality of positive electrode active material 110 particles.

In the positive electrode material 1000, the content of the solid electrolyte 100 and the content of the positive electrode active material 110 may be the same or different.

The positive electrode material 1000 may contain multiple conductive materials 140 .

The positive electrode material 1000 may include multiple first conductive materials 150 and multiple second conductive materials 160 .

<Method for producing positive electrode material>
The positive electrode material 1000 can be manufactured, for example, by the method described below.

The positive electrode active material 110, the solid electrolyte 100 and the conductive material 140 are mixed to produce a mixture of these materials. Conductive material 140 includes first conductive material 150 and second conductive material 160 . For example, after preparing a solvent and the conductive material 140 and mixing the conductive material 140 with the solvent, the positive electrode active material 110 and the solid electrolyte 100 may be added to and mixed with the resulting mixture. Thereby, a positive electrode material 1000 including a mixture of the positive electrode active material 110, the solid electrolyte 100 and the conductive material 140 is obtained.

The method of mixing the positive electrode active material 110, the solid electrolyte 100 and the conductive material 140 is not particularly limited. For example, a machine such as a homogenizer may be used to mix these materials. Uniform mixing can be achieved by using a homogenizer. The mixing ratio of positive electrode active material 110 and solid electrolyte 100 is not particularly limited.

(Modification 1)
FIG. 2 is a cross-sectional view showing a schematic configuration of a positive electrode material 1001 in Modification 1. As shown in FIG. The positive electrode material 1001 further includes a coating layer 120 that covers at least part of the surface of the positive electrode active material 110 . The positive electrode active material 110 at least part of the surface of which is covered with the coating layer 120 is referred to as a "covered positive electrode active material 130". Thus, the positive electrode material 1001 may further include a coating layer 120 covering at least part of the surface of the positive electrode active material 110 . According to the above configuration, the resistance of the battery can be further reduced.

The coating layer 120 is in direct contact with the positive electrode active material 110 .

The material forming the coating layer 120 is hereinafter referred to as "coating material". Coated positive electrode active material 130 in Embodiment 2 includes positive electrode active material 110 and a coating material. The coating material forms the coating layer 120 by being present on at least part of the surface of the positive electrode active material 110 .

The coating layer 120 may evenly cover the positive electrode active material 110 . According to the above configuration, since the positive electrode active material 110 and the coating layer 120 are in close contact with each other, the resistance of the battery can be further reduced.

The coating layer 120 may cover only part of the surface of the positive electrode active material 110 . The particles of the positive electrode active material 110 are in direct contact with each other through the portions not covered with the coating layer 120, thereby improving the electron conductivity between the particles of the positive electrode active material 110. As a result, it becomes possible to operate the battery at a high output.

The coating of the positive electrode active material 110 with the coating layer 120 suppresses the formation of an oxide film due to oxidative decomposition of other solid electrolytes during charging of the battery. As a result, the charging and discharging efficiency of the battery is improved. Another solid electrolyte example is solid electrolyte 100 .

The coating material may contain Li and at least one selected from the group consisting of O, F and Cl.

The coating material is selected from the group consisting of lithium niobate, lithium phosphate, lithium titanate, lithium tungstate, lithium fluorozirconate, lithium fluoroaluminate, lithium fluorotitanate, and lithium fluoromagnesiumate. At least one may be included.

The coating material may be lithium niobate (LiNbO ₃ ).

<Method for producing positive electrode material>
The positive electrode material 1001 can be manufactured by replacing the positive electrode active material 110 with the coated positive electrode active material 130 in the manufacturing method of the positive electrode material 1000 described in the first embodiment.

Here, the coated positive electrode active material 130 can be produced, for example, by the following method. First, the coating layer 120 is formed on the surfaces of the particles of the positive electrode active material 110 . A method for forming the coating layer 120 is not particularly limited. Methods for forming the coating layer 120 include a liquid phase coating method and a vapor phase coating method.

For example, in the liquid phase coating method, a precursor solution of an ion conductive material is applied to the surface of the positive electrode active material 110 . When forming the coating layer 120 containing LiNbO ₃ , the precursor solution can be a mixed solution (sol solution) of a solvent, lithium alkoxide and niobium alkoxide. Lithium alkoxides include lithium ethoxide. Niobium alkoxides include niobium ethoxide. Solvents are, for example, alcohols such as ethanol. The amounts of lithium alkoxide and niobium alkoxide are adjusted according to the target composition of the coating layer 120 . Water may be added to the precursor solution, if desired. The precursor solution may be acidic or alkaline.

The method of applying the precursor solution to the surface of the positive electrode active material 110 is not particularly limited. For example, the precursor solution can be applied to the surface of the cathode active material 110 using a tumbling flow granulation coating apparatus. According to the rolling flow granulation coating apparatus, the precursor solution can be sprayed onto the positive electrode active material 110 while rolling and flowing the positive electrode active material 110 to apply the precursor solution to the surface of the positive electrode active material 110 . . Thereby, a precursor film is formed on the surface of the positive electrode active material 110 . After that, the positive electrode active material 110 coated with the precursor coating is heat-treated. The heat treatment promotes gelation of the precursor coating to form the coating layer 120 . Thereby, the coated positive electrode active material 130 is obtained. At this point, the coating layer 120 covers substantially the entire surface of the positive electrode active material 110 . The thickness of the covering layer 120 is generally uniform.

The vapor phase coating method includes a pulsed laser deposition (PLD) method, a vacuum deposition method, a sputtering method, a thermal chemical vapor deposition (CVD) method, a plasma chemical vapor deposition method, and the like. . For example, in the PLD method, an ion-conducting material as a target is irradiated with a high-energy pulse laser (eg, KrF excimer laser, wavelength: 248 nm) to deposit sublimated ion-conducting material on the surface of the positive electrode active material 110 . When forming the coating layer 120 of LiNbO ₃ , high-density sintered LiNbO ₃ is used as a target.

(Embodiment 2)
Embodiment 2 will be described below. Descriptions overlapping those of the first embodiment are omitted as appropriate.

FIG. 3 is a cross-sectional view showing a schematic configuration of a battery 2000 according to Embodiment 2. FIG.

A battery 2000 according to Embodiment 2 includes a positive electrode 201 , an electrolyte layer 202 and a negative electrode 203 . The positive electrode 201 includes the positive electrode material in Embodiment 1 or Modification 1. Electrolyte layer 202 is positioned between positive electrode 201 and negative electrode 203 . FIG. 3 shows a positive electrode material 1000 as an example of a positive electrode material contained in the positive electrode 201. As shown in FIG.

According to the above configuration, both energy density and electron conductivity can be achieved in the positive electrode 201 . Thereby, the energy density of the battery 2000 can be improved, and the resistance of the battery 2000 can be lowered.

When the positive electrode material is the positive electrode material 1000, the volume ratio "v1:100-v1" between the positive electrode active material 110 and the solid electrolyte 100 contained in the positive electrode 201 may satisfy 30≤v1≤95. Here, v1 represents the volume ratio of the positive electrode active material 110 when the total volume of the positive electrode active material 110 and the solid electrolyte 100 contained in the positive electrode 201 is 100. A sufficient energy density of the battery 2000 can be ensured when 30≦v1 is satisfied. When v1≦95 is satisfied, the battery 2000 can operate at high output.

When the positive electrode material is the positive electrode material 1001, the volume ratio "v11:100-v11" between the coated positive electrode active material 130 and the solid electrolyte 100 contained in the positive electrode 201 may satisfy 30≤v11≤95. Here, v11 represents the volume ratio of the coated positive electrode active material 130 when the total volume of the coated positive electrode active material 130 and the solid electrolyte 100 contained in the positive electrode 201 is 100. When 30≦v11 is satisfied, a sufficient energy density of the battery 2000 can be secured. When v11≦95 is satisfied, the battery 2000 can operate at high output.

The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 201 is 10 μm or more, a sufficient energy density of the battery 2000 can be secured. When the thickness of positive electrode 201 is 500 μm or less, battery 2000 can operate at high output.

The electrolyte layer 202 is a layer containing an electrolyte. The electrolyte is, for example, a solid electrolyte. That is, electrolyte layer 202 may be a solid electrolyte layer. As the solid electrolyte contained in electrolyte layer 202, the material exemplified as solid electrolyte 100 in Embodiment 1 may be used. That is, electrolyte layer 202 may contain a solid electrolyte having the same composition as solid electrolyte 100 . According to the above configuration, the charge/discharge efficiency of the battery 2000 can be further improved.

The electrolyte layer 202 may contain a halide solid electrolyte having a composition different from that of the solid electrolyte 100 .

The electrolyte layer 202 may contain a sulfide solid electrolyte.

The electrolyte layer 202 may contain only one solid electrolyte selected from the materials listed as solid electrolytes.

The electrolyte layer 202 may contain two or more solid electrolytes selected from the materials listed as solid electrolytes. In this case, the plurality of solid electrolytes have compositions different from each other. For example, electrolyte layer 202 may include a halide solid electrolyte and a sulfide solid electrolyte.

The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 202 is 1 μm or more, the short circuit between the positive electrode 201 and the negative electrode 203 is less likely to occur. When the thickness of electrolyte layer 202 is 300 μm or less, battery 2000 can operate at high output.

The negative electrode 203 includes a material that has the property of intercalating and deintercalating metal ions (eg, lithium ions). The negative electrode 203 contains, for example, a negative electrode active material.

Metal materials, carbon materials, oxides, nitrides, tin compounds, silicon compounds, etc. can be used for the negative electrode active material. The metal material may be a single metal. The metal material may be an alloy. Examples of metallic materials include lithium metal, lithium alloys, and the like. Examples of carbon materials include natural graphite, coke, ungraphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. The capacity density can be improved by using silicon (Si), tin (Sn), a silicon compound, a tin compound, or the like.

The negative electrode 203 may contain a solid electrolyte. According to the above configuration, the lithium ion conductivity inside the negative electrode 203 is increased, and the battery 2000 can operate at high output. As the solid electrolyte contained in negative electrode 203, the material exemplified as solid electrolyte 100 in Embodiment 1 may be used. That is, negative electrode 203 may contain a solid electrolyte having the same composition as that of solid electrolyte 100 .

The shape of the solid electrolyte contained in the negative electrode 203 in Embodiment 2 is not particularly limited. The shape of the solid electrolyte contained in the negative electrode 203 may be acicular, spherical, oval, or the like, for example. For example, the shape of the solid electrolyte contained in the negative electrode 203 may be particulate.

When the shape of the solid electrolyte contained in the negative electrode 203 is particulate (for example, spherical), the median diameter of the solid electrolyte may be 100 μm or less. When the solid electrolyte has a median diameter of 100 μm or less, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode 203 . Thereby, the charge/discharge characteristics of the battery 2000 are improved.

The median diameter of the solid electrolyte contained in the negative electrode 203 may be 10 μm or less, or may be 1 μm or less. According to the above configuration, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode 203 .

The median diameter of the solid electrolyte contained in the negative electrode 203 may be smaller than the median diameter of the negative electrode active material. According to the above configuration, the negative electrode active material and the solid electrolyte can form a better dispersion state in the negative electrode 203 .

The shape of the negative electrode active material in Embodiment 2 is not particularly limited. The shape of the negative electrode active material may be, for example, acicular, spherical, or oval. For example, the shape of the negative electrode active material may be particulate.

The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can form a good dispersion state in the negative electrode 203 . Thereby, the charge/discharge characteristics of the battery 2000 are improved. When the median diameter of the negative electrode active material is 100 μm or less, the diffusion rate of lithium in the negative electrode active material is sufficiently ensured. This allows battery 2000 to operate at high output.

The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte contained in the negative electrode 203 . Thereby, the negative electrode active material and the solid electrolyte can form a good dispersed state.

The volume ratio "v2:100-v2" between the negative electrode active material and the solid electrolyte contained in the negative electrode 203 may satisfy 30≤v2≤95. Here, v2 represents the volume ratio of the negative electrode active material when the total volume of the negative electrode active material and the solid electrolyte contained in the negative electrode 203 is taken as 100. A sufficient energy density of the battery 2000 can be ensured when 30≦v2 is satisfied. When v2≦95 is satisfied, the battery 2000 can operate at high output.

The thickness of the negative electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 203 is 10 μm or more, a sufficient energy density of the battery 2000 can be secured. When the thickness of the negative electrode 203 is 500 μm or less, the battery 2000 can operate at high output.

At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving adhesion between particles. A binder is used to improve the binding properties of the material that constitutes the electrode. Binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, poly Acrylate hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid hexyl ester, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, Carboxymethyl cellulose etc. are mentioned. Also selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. Copolymers of two or more materials described above can also be used as binders. A mixture of two or more selected from the above materials may also be used as the binder.

The negative electrode 203 may contain a conductive aid for the purpose of improving electronic conductivity. Examples of conductive aids include graphites such as natural graphite or artificial graphite, carbon blacks such as acetylene black and Ketjen black, conductive fibers such as carbon fiber or metal fiber, carbon fluoride, and metal powder such as aluminum. conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene. Cost reduction can be achieved when a carbon conductive aid is used.

Shapes of the battery 2000 in Embodiment 2 include, for example, a coin shape, a cylindrical shape, a rectangular shape, a sheet shape, a button shape, a flat shape, and a laminated shape.

The details of the present disclosure will be described below using Examples 1 to 9 and Comparative Examples 1 to 5.

<<Example 1>>
[Preparation of sulfide solid electrolyte]
In an argon glove box with a dew point of −60° C. or lower, the raw material powders of Li ₂ S and P ₂ S ₅ were weighed so that the molar ratio of Li ₂ S:P ₂ S ₅ was 75:25. Raw material powders were pulverized and mixed in a mortar to obtain a mixture. Then, using a planetary ball mill (manufactured by Fritsch, model P-7), the mixture was milled at 510 rpm for 10 hours. As a result, a vitreous solid electrolyte was obtained. The obtained solid electrolyte was heat-treated in an inert atmosphere at 270° C. for 2 hours. As a result, Li ₂ SP ₂ S ₅ (hereinafter referred to as LPS) in the form of glass ceramics, which is a sulfide solid electrolyte, was produced.

[Preparation of coated positive electrode active material]
LiNi _0.8 (Co, Mn) _0.2 O ₂ (hereinafter referred to as NCM) was used as a positive electrode active material. LiNbO ₃ was used as the coating material. A coating layer containing LiNbO ₃ was formed by a liquid phase coating method. Specifically, first, a precursor solution of an ion conductive material was applied to the surface of the NCM. This formed a precursor coating on the surface of the NCM. The NCM coated with the precursor coating was then heat treated. Gelation of the precursor film progressed by the heat treatment, and a coating layer made of LiNbO ₃ was formed. A coated positive electrode active material (hereinafter referred to as Nb-NCM) was produced by such a method.

[Preparation of positive electrode material]
Carbon fiber (VGCF-H, manufactured by Showa Denko KK) was used as the first conductive material. The average major axis diameter of VGCF-H was 6 μm. Acetylene black with an average particle size of 23 nm was used as the second conductive material. The binder, solvent, VGCF-H and acetylene black were mixed in an argon glove box with a dew point of −60° C. or less and dispersed using a homogenizer. This gave a mixture of binder, solvent, VGCF-H and acetylene black. The mixing ratio of VGCF-H and acetylene black was 2:0.125 in mass ratio. Nb-NCM as a coating active material and LPS as a solid electrolyte were added to and mixed with the mixture and dispersed with a homogenizer to prepare a slurry containing the positive electrode material. The mixing ratio of Nb-NCM and LPS was 70:30 by volume. "VGCF" is a registered trademark of Showa Denko K.K.

[Preparation of positive electrode]
The positive electrode was produced by apply|coating the produced slurry on a collector, and making it dry on a hotplate.

<<Example 2>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.3 in mass ratio. Other steps were the same as in Example 1, and a positive electrode of Example 2 was obtained.

<<Example 3>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.4 in mass ratio. Other steps were the same as in Example 1, and a positive electrode of Example 3 was obtained.

<<Example 4>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.475 in mass ratio. Other steps were the same as in Example 1, and a positive electrode of Example 4 was obtained.

<<Example 5>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 1.6:0.475 in mass ratio. Other steps were the same as in Example 1, and a positive electrode of Example 5 was obtained.

<<Example 6>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.65 in mass ratio. Other steps were the same as in Example 1, and a positive electrode of Example 6 was obtained.

<<Example 7>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 1.5:0.475 in mass ratio. The mixing ratio of Nb-NCM and LPS was 67:33 by volume. The positive electrode of Example 7 was obtained in the same manner as in Example 1 except for these steps.

<<Example 8>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.3 in mass ratio. The mixing ratio of Nb-NCM and LPS was 72:28 by volume. A positive electrode of Example 8 was obtained in the same manner as in Example 1 except for these steps.

<<Example 9>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0.3 in mass ratio. The mixing ratio of Nb-NCM and LPS was 75:25 by volume. A positive electrode of Example 9 was obtained in the same manner as in Example 1 except for these steps.

<<Comparative Example 1>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2.4:0 in mass ratio. That is, the conductive material of Comparative Example 1 was only VGCF-H. Other steps were the same as in Example 1, and a positive electrode of Comparative Example 1 was obtained.

<<Comparative Example 2>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 2:0 in mass ratio. That is, the conductive material of Comparative Example 2 was only VGCF-H. Other steps were the same as in Example 1, and a positive electrode of Comparative Example 2 was obtained.

<<Comparative Example 3>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 1.6:0 in mass ratio. That is, the conductive material of Comparative Example 3 was only VGCF-H. Other steps were the same as in Example 1, and a positive electrode of Comparative Example 3 was obtained.

<<Comparative Example 4>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 0.8:0 in mass ratio. That is, the conductive material of Comparative Example 4 was only VGCF-H. Other steps were the same as in Example 1, and a positive electrode of Comparative Example 4 was obtained.

<<Comparative Example 5>>
In the manufacturing process of the positive electrode material, the mixing ratio of VGCF-H and acetylene black was 0:0.65 in mass ratio. That is, the conductive material of Comparative Example 5 was only acetylene black. Other steps were the same as in Example 1, and a positive electrode of Comparative Example 5 was obtained.

(Evaluation of electronic conductivity)
Using the positive electrodes of Examples 1 to 9 and Comparative Examples 1 to 5, the electron conductivity was evaluated under the following conditions.

FIG. 4 is a diagram explaining a method for evaluating the electronic conductivity of the positive electrode. Using a facing positive electrode 3000 as shown in FIG. 4, the electronic conductivity of the positive electrode was evaluated at 25°C. The opposing positive electrode 3000 was produced by stacking current collectors 204 on the outer sides of a stack of two positive electrodes 201 facing each other, and then pressing the stack at a high pressure. Al foil was used as the current collector 204 . A potentiostat 400 was connected to the opposing positive electrode 3000 thus obtained, and the electronic resistance was measured by the following procedure.

Voltages of 0.3 V, 0.2 V, -0.2 V, and -0.3 V were applied for 1 minute each by the potentiostat 400, and the current value was read for each. FIG. 5 is a graph showing the correlation between voltage and current value in the facing positive electrode 3000 of Example 1. FIG. The current values were linearly approximated by Ohm's law. The slope of the approximate straight line indicates the DC resistance.

Using the DC resistance value obtained from the slope of the approximate straight line, the electron conductivity σ of the positive electrode of Example 1 was calculated using the following formula (2). Table 1 shows the calculated electronic conductivity.

σ={R×S/(2t)} ⁻¹ (2)

In formula (2), S is the surface area of the positive electrode. R is the DC resistance value obtained from the slope of the approximate straight line. t is the thickness of the positive electrode. The “thickness of the positive electrode” means the thickness of the positive electrode 201 in FIG.

The electron conductivity of the positive electrodes of Examples 2 to 9 and Comparative Examples 1 to 5 was calculated by the same method as above. Table 1 shows the calculated electronic conductivity. In Table 1, VGCF-H (% by mass) represents the mass ratio of VGCF-H when the mass of the positive electrode active material is taken as 100%. Acetylene black (% by mass) represents the mass ratio of acetylene black to the mass of the positive electrode active material as 100%. The total conductive material (% by mass) represents the ratio of the total mass of VGCF-H and acetylene black to the mass of the positive electrode active material as 100%. In Table 1, VGCF-H (% by mass) represents the mass ratio of VGCF-H to the total mass of VGCF-H and acetylene black. Acetylene black (mass %) represents the ratio of the mass of acetylene black to the total mass of VGCF-H and acetylene black.

≪Consideration≫
Examples 1 to 9, which contain VGCF-H and acetylene black as conductive materials, increase the electronic conductivity of the positive electrode compared to Comparative Examples 1 to 5, which contain only one of VGCF-H and acetylene black. showed a trend.

FIG. 6 is a graph showing the electron conductivity of the positive electrodes of Examples 1 to 9 and Comparative Examples 1 to 5. In FIG. 6, the vertical axis indicates the calculated electronic conductivity. The horizontal axis indicates the mass ratio of the conductive material when the mass of the coated positive electrode active material is taken as 100%.

The mass ratio of the conductive material in Example 3 and Comparative Example 1 was the same. However, the electronic conductivity of Example 3 was more than twice the electronic conductivity of Comparative Example 1. That is, when the mass ratio of the conductive material is about the same, the electronic conductivity can be greatly improved.

The electronic conductivity of Example 7 and Comparative Example 1 were comparable. However, the mass ratio of the conductive material of Example 7 was smaller than that of the conductive material of Comparative Example 1. In other words, when the electronic conductivity was the same, the mass ratio of the conductive material could be reduced. This is probably because VGCF-H and acetylene black are easily connected to each other by containing VGCF-H and acetylene black as the conductive material, so that an electron-conducting network is efficiently formed in the positive electrode.

The mass ratios of the conductive materials of Examples 2, 8 and 9 were the same. The volume ratio and electronic conductivity of the coated positive electrode active material increased in the order of Examples 2, 8 and 9. That is, it was possible to improve the electron conductivity with an increase in the volume ratio of the positive electrode active material.

As shown in Examples 2 to 6, the electronic conductivity could be improved with an increase in the mass ratio of acetylene black to the total conductive material.

The battery of the present disclosure can be used, for example, as an all-solid lithium secondary battery.

Reference Signs List

1000, 1001 positive electrode material 100 solid electrolyte 110 positive electrode active material 120 coating layer 130 coated positive electrode active material 140 conductive material 150 first conductive material 160 second conductive material 2000 battery 201 positive electrode 202 electrolyte layer 203 negative electrode 204 current collector 3000 Opposite positive electrode 400 potentiostat

Claims

comprising a mixture of a positive electrode active material, a solid electrolyte and a conductive material;
The conductive material includes a first conductive material having an average major axis diameter of 1 μm or more and a second conductive material having an average particle size of 100 nm or less,
The ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 60% or more and 90% or less.
cathode material.
The ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 65% or more and 85% or less.
The positive electrode material according to claim 1.
The ratio of the volume of the positive electrode active material to the total volume of the positive electrode active material and the solid electrolyte is 67% or more and 75% or less.
The positive electrode material according to claim 1.
When the mass ratio of the positive electrode active material is 100, the mass ratio of the conductive material is 3 or less.
4. The cathode material according to any one of claims 1-3.
The ratio of the mass of the second conductive material to the mass of the conductive material is 80% or less.
5. The cathode material according to any one of claims 1-4.
The ratio of the mass of the second conductive material to the mass of the conductive material is 5% or more and 50% or less.
The positive electrode material according to claim 5.
The ratio of the mass of the second conductive material to the mass of the conductive material is 6% or more and 25% or less.
The positive electrode material according to claim 5.
The first conductive material has an average major axis diameter of 4 μm or more,
8. The cathode material according to any one of claims 1-7.
The second conductive material has an average particle size of 25 nm or less,
The positive electrode material according to claim 8.
the first conductive material and the second conductive material comprise a carbon material;
10. Cathode material according to any one of claims 1-9.
wherein the first conductive material comprises a fibrous carbon material;
11. The cathode material according to any one of claims 1-10.
the second conductive material comprises carbon black;
12. The cathode material according to any one of claims 1-11.
The carbon black includes acetylene black,
The positive electrode material according to claim 12.
The solid electrolyte contains at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte,
14. The cathode material according to any one of claims 1-13.
The positive electrode active material has a layered rock salt structure,
15. The cathode material according to any one of claims 1-14.
Further comprising a coating layer that covers at least part of the surface of the positive electrode active material,
16. Cathode material according to any one of claims 1-15.
a positive electrode comprising the positive electrode material according to any one of claims 1 to 16;
a negative electrode;
an electrolyte layer disposed between the positive electrode and the negative electrode;
with
battery.
The electrolyte layer contains a sulfide solid electrolyte,
18. The battery of Claim 17.